Waveguide antenna structure for intrusion detection apparatus

ABSTRACT

The disclosure includes an intrusion detection unit having a rectangular transmitting waveguide and a corresponding receiving waveguide mounted in stacked relationship within a U-shaped housing member. The forward ends of the waveguides are connected to the housing front wall which extends perpendicularly of the waveguide aperture and defines the energy pattern shaping flanges. The waveguides are mounted in vertically spaced relation and coupled by a coaxial line. A pair of printed circuit boards are secured to the outer sidewall of the stacked waveguides such that the waveguides form the chassis for the transmitter and receiver means. An outer cover telescopes over the housing member to enclose the waveguides and the circuitry. The radiation pattern may be modified by the mounting of a tuning plate behind the shaping flange portion. Releasable plates having an outward flare may also be secured to the front wall to further modify the radiation pattern.

United States Patent 1 Corbell et al.

[451 July 17,1973

[ WAVEGUIDE ANTENNA STRUCTURE FOR INTRUSION DETECTION APPARATUS [75] inventors: Paul I. Corbell, Dallas, Tex.; Alfred Giovanelli, Kenosha; Lawrence B. Korta, Milwaukee, both of Wis.

[73] Assignee: Johnson Service Company,

Milwaukee, Wis.

[22] Filed: Apr. 22, 1971 [211 App]. No.: 136,570

Related US. Application Data [63] Continuation of Ser. No. 805,590, March 10, 1969,

abandoned.

[52] us. on 343/702, 343/8, 343/779 [51] int. (:1. H01q 1/24 [58] Field ofSearch 343/840, 772, 776,

[56] References Cited UNITED STATES PATENTS 5/1970 Bloice 343/8 l/l947 Heim 343/772 Primary Examiner- Eli Lieberman Attorney-Andrus, Sceales, Starke & Sawall [5 7] ABSTRACT The disclosure includes an intrusion detection unit having a rectangular transmitting waveguide and a corresponding receiving waveguide mounted in stacked relationship within a U-shaped housing member. The forward ends of the waveguides are connected to the housing front wall which extends perpendicularly of the waveguide aperture and defines the energy pattern shaping flanges. The waveguides are mounted in vertically spaced relation and coupled by a coaxial line. A pair of printed circuit boards are secured to the outer sidewall of the stacked waveguides such that the waveguides form the chassis for the transmitter and receiver means. An outer cover telescopes over the housing member to enclose the waveguides and the circuitry. The radiation pattern may be modified by the mounting of a tuning plate behind the shaping flange portion. Releasable plates having an outward flare may also be secured to the front wall to further modify the radiation pattern.

10 Claims, 10 Drawing Figures Pmmmm V 3.747.109

SHEEI 1 0F 2 FIG 2 1 7 lib p UW aQ LL ALF-Ran Gav/55m BY LAWRENCE a KORTA ,SLA, fail/W- Attorneys WAVEGUIDE ANTENNA STRUCTURE FOR INTRUSION DETECTION APPARATUS This invention relates to a waveguide antenna apparatus or intrusion detection apparatus and particularly 1 to a waveguide antenna providing a directional radiation pattern.

Detection of intrusion into selected areas has been accomplished by radiating of energy into the area with the intruding person or objects changing the energy distribution. A sensing means senses this distribution change and actuates a suitable alarm or the like. Particularly satisfactory systems have been developed employing the filling of the area with a radio frequency energy field in combination with a receiver for responding to Doppler frequency signals resulting from movement of foreign objects or bodies within the field. For example, U.S. Pat. Nos. 3,242,486 and 3,378,834 to P. Corbell disclose highly satisfactory Doppler frequency detection systems. The first patent particularly discloses a transmitter and receiver mounted adjacent each other with the receiver responding to reflected energy. In the second patent, the receiver and detector are mounted in spaced aligned relation to form a perimeter type protection unit.

Such intrusion detection systems have uniformly employed antennas of the horn type construction. Generally, such antennas provide a particularly satisfactory means for perimeter type mounting in the outer portion of the area and establishing a radio frequency microwave energy field in the X-band of the microwave spectrum. The horn antenna, however, has generally required complicated packaging with a projecting horn portion. The coupling waveguide was normally secured to or within the front wall of the enclosure and the horn protruded outwardly therefrom such that the enclosure does not create an interfering ground plane with respect to the projected field. The combination of the substantial enclosure and protruding horn is not considered particularly desirable from the standpoint of appearance and the like. The design is particularly complicated where the transmitting and receiving antennas are incorporated in a single structure to permit convenient packaging and handling, for example, for systems as shown in the Corbell U.S. Pat. No. 3,242,486.

The transmitters generally employ a high voltage Klystron tube for generating the microwave energy. The copending application of Bailey etal entitled Intrusion Detection Apparatus having Modulated Supervisory Control" which was filed on Mar. 10, 1969, bearing Ser. No. 805,591, now U.S. Pat. No. 3,697,989; and is assigned to the same assignee, discloses a highly satisfactory intrusion detection apparatus including a solid state oscillator for generating R-F energy in the S-band of the microwave spectrum. This has been found to provide a satisfactory energy field for protecting of limited areas but such a system particularly employing the usual transmitting horn would create unacceptable package size.

The present invention is particularly directed to a highly novel and improved wageguide antenna apparatus and integrated circuit enclosure for commercial intrusion detection systems particularly for solid state systems such as disclosed in the referred to application and the like. In accordance with the present invention, a rectangular waveguide terminates in one or more field shaping flanges which project laterally from the wave emitting aperture at substantially ninety degrees. Generally, a rectangular waveguide provides a more or less pancake type radiation pattern which projects as a narrow beam. When packaging within an enclosure, however, the waveguide is subject to distortion by the gound plane phenomena. Applicants, however, realized that this phenomena could advantageously be applied to the packaging of the rectangular waveguide particularly in the lower range of the microwave frequencies. Generally, the areas to be protected are more or less rectangular and most intrusion detection systems employ the horn antenna to establish a corresponding radiation pattern. This is desirable to completely cover the area and rapidly detect any movement any place within the room. Applicants determined that whereas an infinite or semi-infinite ground plane construction mounted adjacent the aperture would substantially widen the radiation pattern, a controlled finite flange to the side of the aperture can correspondingly increase and thus control the side lobe to properly distribute the energy and provide a highly satisfactory coverage of a selected area. The radiation pattern is de pendent upon the length of the lateral extending flange, and similar to a horn also on any angular relationship. The flanges may therefore be provided with some outward flare to modify the particular pattern of radiation.

Applicant has found that the construction of a rectangular waveguide terminating in a laterally extending ground plane flange is therefore particularly suitable for establishing the relatively low microwave frequency energy field in the S-band frequencies. Although this requires a waveguide of a significant. dimension, the waveguide may conveniently extend through the waveguide enclosure or housing with the front wall of the housing serving as the shaping flanges. This is particularly advantageous where both a transmitting and receiving waveguide are housed in a single packaged unit. The present invention thus permits compact and esthetically pleasing packaging for commercial application.

Generally, applicant has found that a shaping flange to both sides of the aperture and generally of the same order as the antenna aperture produces a more or less square configuration corresponding to the desired radiation pattern for commercially demanded intrusion detection apparatus and the like.

In accordance with another aspect of the present invention, the particular radiation pattern may be controlled by the mounting of a plate of a larger configuration. The distance between the plat-e and the flange further controls the radiation pattern.

In accordance with a particularly novel aspect of the present invention, the transmitting waveguide and a receiving waveguide are mounted in stacked relationship with the forward ends connected to a housing front wall defining the pattern shaping flanges. The waveguides are mounted in slightly vertically spaced relation to essentially eliminate leakage coupling between the two waveguides. A printed circuit board is secured to at least one outer sidewall of the stacked waveguides such that the waveguide forms the physical supporting structure or chassis for the transmitter and receiver means. The outer cover of the enclosure need only be of a suitable sheet metal or the like to provide an environmental protective enclosure for the circuitry and to provide a decorative enclosure. The board or boards are attached to the waveguide with the securement means in an area of minimum electric field to essentially prevent interfering with the energy field in the waveguide. A coaxial cable or the like couples the waveguides for introducing the reference r-f signal and crystal bias signal and may also provide a supervisory control signal into the receiving waveguide. The waveguide separation and controlled introduction of the bias signalinto the receiving waveguide permits compensation for the tolerance in commercially available detector crystals and the like.

The present invention has been found to provide a highly desirable waveguide antenna structure for intrusion detectionapparatus and particularly provides for.

a compact and inexpensive enclosure which may include essentially planar or flush walls.

The drawings furnished herewith illustrate the best mode presently contemplated by the inventors for carrying out the subject invention and clearly disclose the above advantages and features as well as others which will be readily understood from the following description.

In the drawings:

FIG. 1 is a pictorial view of an intrusion apparatus constructed in accordance with the teaching of the present invention and diagrammatically showing the transmitted and reflected field established by a moving target;

FIG. 2 is a front view of an integrated transmitter and receiver unit shown in FIG. 1 with parts broken away to show structural details;

FIG. 3 is a longitudinal vertical section taken generally on line 3-3 of FIG. 2;

FIG. 4 is a side view of the unit with parts broken away to show structural detail;

FIG. 5 is a view similar to FIG. 4 from the opposite side of the unit;

FIG. 6 is a top view with parts broken away to show structural details;

FIG. 7 is a top diagrammatic view showing the detection pattern obtained with the transmitting antenna of FIG. 1-3;

FIG. 8 is a diagrammatic side view generally illustrating the vertical or I-I-plane of the field;

FIG. 9 is a diagrammatic view similar to FIG. 4 illustrating the addition of a control plate to the structure of FIG. 4; and

FIG. 10 is a pictorial view showing a modification to the structure of FIG. 1 with purposes of further modifying the radiation pattern.

Referring to the drawings and particularly to FIG. 1, the present invention is particularly disclosed in connection with a microwave energy intrusion detection system including an intrusion unit or apparatus 1 which is adapted to be mounted adjacent the perimeter of a room, warehouse building or the like which is to be protected. The intrusion detection apparatus 1 includes a transmitting aperture 2 adapted to produce a field beam 3 of microwave energy which will essentially completely fill the area to be protected. The apparatus further includes a receiving aperture 4 which is adapted to receive reflected energy, shown by beam 5, from a body ortarget 51: within the energy beam 3. The present invention particularly employs the Doppler principle or effect wherein a moving body within the field 3 results in a Doppler frequency signal in the receiving aperture 4. The Doppler frequency is utilized to operate an alarm or other indicating means for detecting the presence of the intruding body.

More particularly, referring to FIGS. 2 and 3, apparatus l, which is specially constructed in accordance with the teaching of the present invention, includes an open ended rectangular waveguide 6 terminating in the transmitting aperture 2. The rectangular waveguide 6 is mounted with the long dimension extending vertically and the narrow dimension in the horizontal or lateral direction. The waveguide 6 is provided with a suitable field exciter unit 7 which is adapted to establish electric and associated magnetic fields within the waveguide 6. The electric field extends in the horizontal direction across the narrow dimension of therectangular waveguide and the beam 3 is emitted or projected as a horizontally polarized beam from the opening 2. The exciter unit 7 is energized from a suitable radio frequency transmitter which is diagrammatically shown in FIG. 2 in block diagram and identified as a suitable solid state excitation circuit assembly 8 which permits compact packaging and long life operation. The circuit assembly is desirably a solid state oscillator unit such as disclosed in the previously identified copending application which establishes a relatively low microwave frequency and field; for example, the transmitter has been satisfactorily operated at 2.45 GH (gigahertz). The Doppler frequencies detected included a range of l to H The particular circuitry employed is not therefore described in any further detail.

A similar rectangular waveguide 9 having a corresponding cross-section is mounted in spaced vertical alignment with the waveguide 6 and terminates in the receiving aperture 4. A crystal detector and mixer unit 10 is secured to the waveguide 9 and interconnected to transmit the received signals to the amplifier 11 which is also diagrammatically shown. The radio frequency detector and mixer of unit 10 may be of any suitable construction such as a crystal detector interconnected to the input of a solid state amplifier and rectifier circuit. Thus, the RF detector and mixer as well as a related alarm and supervisory circuitry may be con-' structed in accordance with the teaching and disclosure of the Corbell US. Pat. No. 3,242,486 and/or the previously identified copending application of Bailey et al entitled Intrusion Detection Apparatus having Modulated Supervisory Control."

The rectangular waveguides 6 and 9, as more fully described herein, are particularly adapted in accordance with the present invention to operate in the S- band frequencies of the microwave spectrum.

The illustrated waveguides 6 and 9 are essentially identical in construction and are mounted in vertically stacked relationship within an outer housing to form an integrated structure in accordance with the present invention as follows. The housing includes a U-shaped base portion 12 having a bottom section or wall 13 and a back section or wall 14 extending perpendicularly from the back edge and a front section or wall 15 similarly projecting upwardly from the front edge. The U- shaped base portion I2 is constructed with the walls 14 p and 15 spaced in accordance with the required length of the waveguides 6 and 9. The waveguides include similarly open-ended rectangular body members mounted in the desired vertically spaced stacked relationship between the walls 14 and I5 as at 16. The back end of the waveguides are spot welded or otherwise secured as at 17 to the back wall 14. The back or outer end of the waveguides are thereby short circuited to create propagation down the wave guide and from the opening into the area to be protected. The forward ends of the waveguides 6 and 9 are similarly secured by the welds 18 to the front section or wall which in turn has apertures corresponding to the cross-section of the waveguides to define the waveguide apertures 2 and 4 which may be covered to prevent entrance of dirt and the like with foam plastic plugs 17a or other suitable low less material. The depth of the front and back walls is selected to be slightly larger than the depth of the aligned waveguides 6 and 9 to permit vertical spacing 16 therebetween and provide a slight frame at the upper and lower edge of the front wall. The width of the housing wall is selected such that the lateral portions extending outwardly from the edge of the apertures generally correspond to the width of the apertures. The lateral extensions or flanges 19 and 20 define finite pattern shaping elements which have been found by proper selection to modify the pattern of a rectangular waveguide to a desired radiation pattern particularly for incorporation into an intrusion detection apparatus. Furthermore, the lateral extending planar flanges 19 and 20 provide a planar or flush front wall for the outer housing of the unit 1 which can be en closed in the illustrated embodiment, for example, by a downwardly telescoping U-shaped cover 21. The U- shaped cover 21 is spaced from the lateral sidewalls of the waveguides 6 and 9 and thus defines a pair of chambers within which the components and circuit connections for the transmitter 8 and the detector and mixer 11 can be conveniently and compactly mounted. The result is that the intrusion apparatus 1 is incorporated as a compact, neat appearing apparatus which is portable and can be conveniently mounted in any desired area. Such appearance is of practical significance where the apparatus is to be employed in the protection of certain rooms and the like.

Although the housing is shown as a generally rectangular housing having a depth generally corresponding to the length of the waveguides, the back wall may be spaced further outwardly with separate enclosure walls provided for shorting of the inner ends of the waveguides 6 and 9. Similarly, the sidewalls may be formed as other than planar members and may be separately formed and interconnected in any desired manner. The generally rectangular housing illustrated in the drawing provides a highly acceptable appearance while establishing a relatively low cost construction. As previously noted, the waveguides 6 and 9 are mounted in slightly spaced vertical relationship. The space 16 essentially decouples the waveguides preventing leakage transfer of energy and the like.

The present invention preferably employs a supervisory or interlock control such as disclosed in the Corbcll US. Pat. No. 3,242,486 wherein a portion of the transmitted energy is fed directly to the receiving antenna waveguide and introduces a modulating signal which is integrated or otherwise detected to insure proper and continued operation of the system. A particularly satisfactory system is shown in the previously referred to eopending application of Bailey et al.

In the illustrated embodiment of the invention, a spe cial coaxial coupling line 22 terminates in end probes connected respectively to the waveguide 6 and the waveguide 9 as at 23 and 24. The line 22 transmits and mixes a portion of the energy of the waveguide 6 with the energy in the waveguide 9 to establish reference r-f signal and if desired a supervisory signal in the detector and mixer unit 110.

In the illustrated embodiment of the invention, the waveguides 6 and 9 are formed as rigid metal wall members. The laterally central location in the housing defines similar chambers to opposite sides thereof. in the illustrated embodiment of the invention, as most clearly shown in FIGS. 2 and 46, the circuit boards 25 and 26 are disposed to the opposite sides of the waveguides and each is generally of a square configuration. The board 25 is disposed to one side of the coupling line 22 and below the coupling waveguide exciter unit 7 and extends from the lower end of the waveguide 9 over the lower portion of waveguide 6 and is bolted by four corner bolts 27 to the adjacent waveguides. Bolts 27 pass through suitable openings in the four corners of the circuit board 25 and are threaded into suitable tapped openings 28 extending through the lower sidewall portion in the waveguides 6 and 9. Tubular spacing members 29 encircle the bolts 27 between the board and the adjacent portions of the waveguides to space the circuit board from the side surface of the waveguides 6 and 9 and the adjacent sidewall of the U- shaped cover 21. The circuit components of the transmitter 8 are connected to the exterior of the circuit board 25 and the circuit interconnections may be formed theron in accordance with the usual printed cireuit technique.

The circuit board 26 is similarly a rectangular member bolted to the opposite side of the waveguides 6 and 9 above the slot fed pickup unit 1(0.'The board 26 is as long as the waveguides and extends downwardly from the upper side portion of waveguide 6 to the upper side portion of waveguide 9. The circuit components 11 of the receiver unit are secured to the exterior of board 26 with the internal connection through a printed circuit or the like.

This results in a very compact, convenient and economieal construction. Thus, the cover material can be formed of any inexpensive sheet metal or the like as it does not support any weight. For example, an intrusion detection system operating at the S-band frequency of 2.45 GH, and constructed as shown in FIGS. 1-6 ineluded rectangular metal tubes which were 7 inches long for'the waveguides. Each tube had a vertical dimension or heighth of 2% inches and a width of 1% inches. The waveguides were spaced approximately 1 inch apart. Each flange l9 and 20 similarly projected outwardly 2% inches from the apertures and had a vertical dimension of 7 inches. The total enclosure was therefore of the order of 7 inches square and the charm bers to the opposite sides of the waveguides provided completely adequate space for mounting of the transmitting and receiving circuitry within the housing.

As previously noted in the illustrated embodiment of the invention, the boards are secured to the waveguides through bolts 27 extending into threaded. openings in the sidewalls of the waveguides. The interconnecting bolts 27 are located immediately adjacent the edges of the waveguides and thus are in an area of minimum electric field. Consequently, the slight discontinuity in the inner surface does not interfere or significantly effect the operation of the waveguide elements. in fact, applicant has found that with the illustrated location of the. threaded openings 28, the bolts may extend through the openings to provide a firm interconnection of the circuit boards. The bolts are clipped flush with the inner wall of the waveguide without interfering with a practical and highly effective waveguide operation.

Referring particularly to FIGS. 7 and 8, a detection pattern 30 is shown for a rectangular waveguide terminating in the normal front wall ears or flanges. The illustrated pattern is not proportionally shown with respect to the flanges. For example, the ears may be of the order of a couple of inches and the pattern length of the order of 70 feet. Generally, the flanges 19 ans 20 tend to laterally expand the side lobe portions of the pattern 30 and thus extend the width of the pattern. Thus, if the shaping flanges are not employed and a generally infinite ground plane is provided, an essentially round configuration is obtained as shown by the dashed lines. Applicant has found that the extension of the side lobes or the use of the essentially laterally projecting flanges improves the radiation detection within a generally rectangular area.

Referring particularly to FIG. 8, the use of the rectangular waveguide with the laterally or transversely extending ears results in a somewhat tear drop shaped field. By proper location, thus the input energy is more or less concentrated in the area shown by the radiation pattern of FIGS. 4 and 5. This pattern can be located at a level generally corresponding to the average level of the intruder and thus provides a very sensitive response. The pattern outlined as shown is not intended to indicate that in fact the pattern is that distinct. In fact, the total area of a room or warehouse is totally filled with the radiated energy field primarily as a result of the reflective nature of the walls such that the movement in any area will be detected. The type construction of the field provided by the rectangular open ended waveguide, however, does produce maximum sensitivity to the most significant portion of the area being protected and the instrusion of a body most likely to be encountered.

The front ears or flanges provide a particular radiation pattern. If it is desired to change the pattern, the flange construction can of course be varied. Alternatively, a tuningplate 31 can be provided as shown in FIG. 9. The elements of FIG. 9 corresponding to the previous described embodiment are similarly numbered for simplicity and clarity of explanation. In FIG. 9, the waveguides project'through a tuning plate 31 which is somewhat larger than the front wall of the housing. The tuning plate 31 defines'a semi-infinite ground plane. The lobe extension of the radiation pattern is a-function of the spacing between the tuning plate 31 and the front wall flanges l9 and 20. The tuning plate 31 will generally cause the lobes to project outwardly beyond the edge of the flange with the outward extension increasing as the plate 33 approaches the flanges.

Furthermore, the angular relationship of the flanges l9 and 20 will, of course, have some effect on the particular pattern configuration for the same reason that the horn antenna is employed to shape the radiation pattern. Thus, in accordance with the present invention, auxiliary attachment plates 32 might be provided as shown in FIG. which can be readily attached or removed from the front wall of the housing to further shape the pattern. In the illustrated embodiment of the invention, the attachment plates 32 are provided with planar mounting flanges'32 which are releasably attached to the front wall immediately adjacent the apertures and waveguides as by mounting screws. The tuning plates 32 extend outwardly at a slight angle with respect to the mounting wall. Generally, however, the attachment plates generally will have only a minimum angle of projection and maintain an essentially perpendicular projection with respect to the energy field. It thus maintains the compact and neat appearing construction.

The present invention thus provides a highly improved antenna structure and component enclosure which can be formed as an integrated unit with a resulting compactness and ease of handling. Furthermore, the construction of the enclosure minimizes the cost, and thus is particularly adapted to commercial production.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims, particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

We claim:

1. An intrusion detection apparatus for detecting intrusion of a member within an area, comprising a support, a microwave transmitter for establishing a selected microwave field, a metal waveguide coupled to said transmitter and having a rectangular cross-section defined by parallel top and bottom walls and parallel sidewalls and terminating in a corresponding rectangular opening having the same cross-section as the wave guide and operating with a transverse electric field and a horizontally polarized projection beam projected directly outwardly from said rectangular opening into said area to be protected, a laterally extending fixed ground plane flange connected to the waveguide closely adjacent to each long edge of the waveguide opening and extending outwardly from said edge at substantially a right angle to the opening of the waveguide, each flange substantially corresponding in size and configuration to said rectangular opening and defining a pattern shaping means selected to create a predetermined lateral expansion and projection of said beam to produce said selected field within said area to be protected, and a microwave receiving means mounted to intercept reflection of said beam from a member within said area and thereby responding to movement of an intruding member in said field to detect intrusion therein. 2. The intrusion detection apparatus of claim I, having a second similar waveguide located in stacked aligned relation with'the first waveguide and in a corresponding orientation, said receiving means being coulpled to said second waveguide to respond to signals generated by interruption of said beam, and said ground plane flange member being similarly connected to both of said waveguides.

3. The intrusion detection apparatus of claim 2. wherein said waveguides are being mounted in aligned closely spaced relation, and an energy coupling means is connected between said waveguides to positively transmit a portion of the energy from the one waveguide to the other.

4. The intrusion detection apparatus of claim 1 wherein said flange member supports auciliary attachment plates which extend outwardly with respect to the plane of said waveguide opening at a selected angle therefrom.

5. The intrusion detection of claim 1 having a housing which is rectangular with a sidewall spaced in accordance with the width of the flange member and closed by said flange member to define a chamber, and circuit support means secured to the waveguide within said chamber.

6. The intrusion detection of claim 1, having a second similar waveguide located in stacked relation with the first waveguide and in a corresponding orientation, said receiving means being coupled to said second waveguide to respond to signals generated by interruption of said beam, a metal housing member enclosing said waveguides and having a pair of spaced sidewalls and a front wall terminating'at said sidewalls with apertures corresponding to and spaced in accordance with said waveguides, means to secure the waveguides within the housing with the forward end connected to the front wall in alignment with the apertures, said front wall to the opposite sides of the aperture being defined by said laterally extending flange member to one side of said waveguide openings and a second corresponding flange member to the opposite side of the waveguide openings.

7. The intrusion detection apparatus of claim 6 having circuit board means attached to the exterior sidewalls of the waveguides and constituting the mounting means for circuit components.

8. The intrusion detection apparatus of claim 1, having a second similar waveguide located in stacked relation with the first waveguide and in a corresponding orientation, said receiving means coupled to said second waveguide to respond to signals generated by interruption of said beam, a generally U-shaped metal housing member of a lengh corresponding to the waveguide and having a rear wall and a spaced front wall with apertures corresponding to and spaced in accordance with said waveguides, means to secure the waveguides within the housing with the opposite ends connected to the front and rear walls in alignment with the apertures, said front wall to the opposite sides of the apertures generally conforming to the size of the apertures and being defined by said laterally extending flange member to one side of said waveguide opening and a second corresponding ground plane flange member to the opposite side of the waveguide opening, sidewalls secured to the edges of the rear wall and front wall to define a closed enclosure, and circuit board means attached to the exterior sidewalls of the waveguides between the waveguides and the housing and constituting the mounting means for circuit components.

9. The intrusion detection apparatus of claim I, having a control flange member disposed behind the ground plane flange member and being larger than said ground plane flange member.

10. An antenna structure forming a part of an intrusion detection apparatus for establishing a selected field, said structure and apparatus: comprising a waveguide having a rectangular cross section terminating in a corresponding opening for operating with a transverse electric field and a horizontally polarized progation beam, at least one laterally extending flange member connected closely adjacent to the edge of the waveguide opening and extending outwardly from said edge at substantially a right angle to the opening of the waveguide and defining a pattern shaping means, a second similar waveguide located in stacked relation with the first waveguide and in a corresponding orientation, a receiving means coupled to said second waveguide to respond to signals generated by interruption of said beam, a generally U-shaped metal housing member of a length corresponding to the waveguide and having a front wall with apertures corresponding to and spaced in accordance with said waveguides, means to secure the waveguides within the housing with the opposite ends connected to the front and rear walls in alignment with the apertures, said front wall to the opposite sides of the apertures generally conforming to the size of the apertures and defining corresponding flange members, sidewalls secured to the edges of the rear wall and front wall, circuit board means attached to the exterior sidewalls of the waveguides and constituting the mounting means for circuit components, and a cover means secured to the housing to define a closed enclosure.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,747 109 Dated July 1'? 1973 lnventofl Paul I. Corbell et a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 51, after "having" delete "Modulated" Column L line 1+6, after "having" delete "Modu" line L1], before "Supervisory" delete "lated".

Signed and sealed this 25th day of June 197M.

(SEAL) Attest:

C. MARSHALL DANN EDWARD M.FLETCHER,JR.

Commissioner of Patents Attesting Officer USCOMM'DC 6037 6-P69 FORM PC3-1950 (10-69) v u.s. eovznuuzm- PRINTING orncz: mes o-ass-zu.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 5714.7 109 Dated July 17 1973 Invent0r(s) Paul I. COIbGll St 8.1-

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line El, after- "having" delete "Modulated" Column Lt, line 1+6, after "having" delete "Modu' line [4.7, before Superv-isory" delete "lated".

Signed and sealed this 25th day of June 197M.

(SEAL) Attest:

C. MARSHALL DANN EDWARD M.FLETCHER,JR.

Commissioner of Patents Attesting Officer FORM PC4950 (169) USCOMM-DC 60376-P69 [1.5. GOVERNMENT PRINTING OFFICE: I95, 0-365-334 

1. An intrusion detection apparatus for detecting intrusion of a member within an area, comprising a support, a microwave transmitter for establishing a selected microwave field, a metal waveguide coupled to said transmitter and having a rectangular cross-section defined by parallel top and bottom walls and parallel sidewalls and terminating in a corresponding rectangular opening having the same cross-section as the waveguide and operating with a transverse electric field and a horizontally polarized projection beam projected directly outwardly from said rectangular opening into said area to be protected, a laterally extending fixed ground plane flange connected to the waveguide closely adjacent to each long edge of the waveguide opening and extending outwardly from said edge at substantially a right angle to the opening of the waveguide, each flange substantially corresponding in size and configuration to said rectangular opening and defining a pattern shaping means selected to create a predetermined lateral expansion and projection of said beam to produce said selected fiEld within said area to be protected, and a microwave receiving means mounted to intercept reflection of said beam from a member within said area and thereby responding to movement of an intruding member in said field to detect intrusion therein.
 2. The intrusion detection apparatus of claim 1, having a second similar waveguide located in stacked aligned relation with the first waveguide and in a corresponding orientation, said receiving means being coupled to said second waveguide to respond to signals generated by interruption of said beam, and said ground plane flange member being similarly connected to both of said waveguides.
 3. The intrusion detection apparatus of claim 2, wherein said waveguides are being mounted in aligned closely spaced relation, and an energy coupling means is connected between said waveguides to positively transmit a portion of the energy from the one waveguide to the other.
 4. The intrusion detection apparatus of claim 1 wherein said flange member supports auciliary attachment plates which extend outwardly with respect to the plane of said waveguide opening at a selected angle therefrom.
 5. The intrusion detection of claim 1 having a housing which is rectangular with a sidewall spaced in accordance with the width of the flange member and closed by said flange member to define a chamber, and circuit support means secured to the waveguide within said chamber.
 6. The intrusion detection of claim 1, having a second similar waveguide located in stacked relation with the first waveguide and in a corresponding orientation, said receiving means being coupled to said second waveguide to respond to signals generated by interruption of said beam, a metal housing member enclosing said waveguides and having a pair of spaced sidewalls and a front wall terminating at said sidewalls with apertures corresponding to and spaced in accordance with said waveguides, means to secure the waveguides within the housing with the forward end connected to the front wall in alignment with the apertures, said front wall to the opposite sides of the aperture being defined by said laterally extending flange member to one side of said waveguide openings and a second corresponding flange member to the opposite side of the waveguide openings.
 7. The intrusion detection apparatus of claim 6 having circuit board means attached to the exterior sidewalls of the waveguides and constituting the mounting means for circuit components.
 8. The intrusion detection apparatus of claim 1, having a second similar waveguide located in stacked relation with the first waveguide and in a corresponding orientation, said receiving means coupled to said second waveguide to respond to signals generated by interruption of said beam, a generally U-shaped metal housing member of a lengh corresponding to the waveguide and having a rear wall and a spaced front wall with apertures corresponding to and spaced in accordance with said waveguides, means to secure the waveguides within the housing with the opposite ends connected to the front and rear walls in alignment with the apertures, said front wall to the opposite sides of the apertures generally conforming to the size of the apertures and being defined by said laterally extending flange member to one side of said waveguide opening and a second corresponding ground plane flange member to the opposite side of the waveguide opening, sidewalls secured to the edges of the rear wall and front wall to define a closed enclosure, and circuit board means attached to the exterior sidewalls of the waveguides between the waveguides and the housing and constituting the mounting means for circuit components.
 9. The intrusion detection apparatus of claim 1, having a control flange member disposed behind the ground plane flange member and being larger than said ground plane flange member.
 10. An antenna structure forming a part of an intrusion detection apparatus for establishing a selected field, said structure and apparatus comprising a waveguIde having a rectangular cross section terminating in a corresponding opening for operating with a transverse electric field and a horizontally polarized progation beam, at least one laterally extending flange member connected closely adjacent to the edge of the waveguide opening and extending outwardly from said edge at substantially a right angle to the opening of the waveguide and defining a pattern shaping means, a second similar waveguide located in stacked relation with the first waveguide and in a corresponding orientation, a receiving means coupled to said second waveguide to respond to signals generated by interruption of said beam, a generally U-shaped metal housing member of a length corresponding to the waveguide and having a front wall with apertures corresponding to and spaced in accordance with said waveguides, means to secure the waveguides within the housing with the opposite ends connected to the front and rear walls in alignment with the apertures, said front wall to the opposite sides of the apertures generally conforming to the size of the apertures and defining corresponding flange members, sidewalls secured to the edges of the rear wall and front wall, circuit board means attached to the exterior sidewalls of the waveguides and constituting the mounting means for circuit components, and a cover means secured to the housing to define a closed enclosure. 